Polar Diagrams RNAV

The polar diagram shows the point at which signal strength is equal. A useful way to think of this is to imagine that the strength is at 100% at the aerial itself, but that the strength is at 50% (or some other figure) where lines of the polar diagram are.

This provides a visual representation of how the aerial is transmitting the wave. So for a dipole aerial, the signal is omnidirectional and so the place where the signal strength is at 50% is a circle. For a directional antenna, the wave is focussed mainly in one direction, so will take longer to drop to 50% strength in the direction it is focussed.